Insight into the influence of terminal ligands on magnetic exchange coupling in a series of dimeric copper(II) acetate adducts

A combination of experimental (SQUID magnetometry) and quantum-chemical (BS-DFT, CASSCF(n,m)/NEVPT2, DDCI3) methods is used to probe the influence of terminal ligands on magnetic exchange coupling in the series of [Cu-2(mu(2)-OAc)(4)L-2] complexes with O-donor terminal ligands extended by two novel complexes containing phosphine oxide ligands. The possibilities and limitations of these approaches are discussed. The influence of terminal ligands on magnetic superexchange interaction was quantified by two contributions-the first contribution is associated with structural changes within the {Cu(mu(2)-OAc)(4)Cu} core, while the second contribution is due to the difference in the electronic influence of different terminal ligands at a given core geometry. Both contributions were found to be approximately of the same order of magnitude. These results indicate that magnetic exchange coupling, known to be highly sensitive to the distortions in core geometry, is not solely determined by the core structure. Our findings are consistent with the fact that various one- and multiparameter magnetostructural correlations reported in the literature have only a qualitative predictive capability.